delta_e_map — IMGMETRICS colordiff op

• Data kinds: rgbimage × rgbimage → image2d

• Call: import fullseye as fs; fs.ledger.delta_e_map(rgb1, rgb2, kind='2000', white=(0.95047, 1.0, 1.08883)) (to call the implementation directly, import imgmetrics; imgmetrics.delta_e_map(rgb1, rgb2, kind='2000', white=(0.95047, 1.0, 1.08883)); from the registry, opsimgmetrics.get("delta_e_map"))

Usage

Per-pixel colour-difference map between two sRGB images.

The entry point for looking at perceptual colour difference rather than RGB mean squared error. kind is "2000" (default) or "76".

Procedure: convert the 2 images to Lab with rgb_to_lab(·, white), then per pixel take delta_e_2000 (CIEDE2000, kL = kC = kH = 1) for kind="2000", or delta_e_76 (Euclidean distance in Lab) for "76".

• rgb1, rgb2: same shape with ndim >= 3, last axis 3 ((H, W, 3)). Integer dtypes are normalised by the dtype maximum, float must be in [0, 1] (per the rgb_to_xyz contract). Pass sRGB, not linear RGB.

• white: the Lab white point (default D65).

• Return value: float64 of shape (H, W). 0 means identical colours. Taking the mean gives a whole-image metric (passing channel_axis to compare_images includes it as delta_e_2000_mean).

• Failure (MetricContractError): kind is not one of the above / shapes differ / not 3 channels / float outside [0, 1]. Grey (H, W) is not accepted.

Detailed usage guide

• image_difference_metrics family guide

Background guides (the physics and conventions behind this op)

• colorimetry — Colorimetry and spectra — colour is fixed only by spectrum × illuminant × observer

References (sample data, literature)

• Sample-data catalog (download URLs / licences) — 2-D uses skimage.data (BSD/public domain) plus synthetic images; 3-D lists download URLs for real data sources (Stanford, PDS, …).

• Operator provenance and references — the sources of the research/methods this op family came from.

• The canonical algorithm (author, year) and its uses are named in the family usage guide above.

Runnable examples (verified samples that actually call this op)

• color_transport — py -3.11 examples/color_transport.py

• image_quality_metrics — py -3.11 examples/image_quality_metrics.py

• poc_colormap_readability — py -3.11 examples/poc_colormap_readability.py

• poc_pigment_unmixing — py -3.11 examples/poc_pigment_unmixing.py

• poc_white_balance — py -3.11 examples/poc_white_balance.py

Ops the type connects to (they accept image2d as input)

mse · rmse · psnr · ssim · ms_ssim · ssim_map · image_entropy · joint_entropy

Same category (colordiff)

delta_e_2000 · delta_e_76

*Provenance: imgmetrics.py — IMGMETRICS operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*

© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.